An appliance leakage current interrupter (ALCI), also known as a leakage current interrupter or a ground fault interrupter, is a known type of safety device used in numerous electrically powered appliances. As used throughout this specification (including claims), “appliance” includes electronic devices such as computers, gaming consoles, stereos, televisions, etc. Typically, an ALCI includes a sensor coil that surrounds the hot and neutral wires of the AC mains power supply lines to an appliance. If the current flowing in one line equals the current flowing out of the other line, the magnetic fluxes associated with the two currents will cancel each other out, and no voltage will be induced in the sensor coil. However, if the current flowing in one of the lines is less than the current in the other line (which is indicative of an undesirable grounding through a user or otherwise), the magnetic fluxes will be unequal. A voltage is thereby induced in the sensor coil. Upon detection of such a voltage above a predetermined level, a solenoid or other type of switch is activated (or “tripped”) and a connection in one or both of the lines is broken.
ALCIs perform an important safety function, and are often required for various product certifications. However, there are many conditions under which an ALCI might not trip, but in which it would still be desirable to de-energize an appliance. For example, many electronic devices can only tolerate limited variations in the amount of voltage supplied to the device. Generally speaking, variations in a household voltage level will not trip an ALCI. To protect against such variations, it is usually necessary to provide a separate surge protector
Although useful, surge protectors also have limitations. In particular, surge protectors are typically designed to prevent damage caused by short-term, high level increases in voltage (such as might be expected because of a lightning strike). However, longer term, lower magnitude voltage rises can also cause problems. Surge protectors do not always protect a device from voltage “swells,” e.g., voltage increases of approximately 150% of normal that last for hundreds of milliseconds.
A related concern involves the amount of current drawn by an appliance or other device. Because power is equal to the product of current and voltage, a high current draw under higher input voltages may be problematic, but that same current draw under a lesser voltage may be allowable. Although current-limiting components are available, such components generally prevent current from exceeding a specific level, which level is not variable based on the voltage level. Using known components, it is necessary to assume the highest expected voltage level and limit current to a level that is lower than what might be tolerable under many conditions.
For these and other reasons, there remains a need for components to limit the amount of voltage and/or current supplied to an appliance. If these components could be combined with an ALCI, further advantages would be possible. For example, certain parts of the ALCI could also be used for the voltage and or current limitation functions, thereby reducing cost. Moreover, adding current and/or voltage limiting components to an ALCI would facilitate placing of multiple power control features in a compact package.